docs: def mol(self):
          """ Return record in MOL format """
          if self._mol is None:
              apiurl = 'http://www.chemspider.com/MassSpecAPI.asmx/GetRecordMol?csid=%s&calc3d=false&token=%s' % (self.csid,TOKEN)
              response = urlopen(apiurl)
              tree = ET.parse(response)
              self._mol = tree.getroot().text
          return self._mol